Telephone system



Nov. 22, 1938. J. wlcKs TELEPHONE SYSTEM Filed May 3, 1937 3 Sheets-Sheet 1 INVENTOR. JOHN wlcKs BYDM'A., JM@ nmz,

ATTORNEYS.

Nov. 22, 1938. J, wlcKs 2,137,517

TELEPHONE SYSTEM Filed May 5, 1957 5 Sheets-Sheet 2 zNvENIoR. JOHN wlCKs BYOQM, 'my, 5mg sxfs.,

ATTORNEYS.

Nov. 22, 1938. J. WICKS TELEPHONE SYSTEM Filed May 3, 1937 3 Sheets-Sheet 3 INVBNTOR.

JOHN wlcKs BY @am lla-7, SMZAJM/ ATTORNEY5 Patented Nov. 22, 193s 2,137,517

UNITED STATES PATENT OFFICE TELEPHONE SYSTEM John Wicks, Oak Park, Ill.,` assignor to Associated Electric Laboratories, Inc., Chicago, Ill., a. corporation of Delaware Application May 3, 1937, serial No. 140,317

29 claims. (ci. 179-21) The present invention relates to signalling sysand the bars are not sulciently positive to insure tems and more particularly to automatic switches completely faithful operation oi the switch.

of the so-called cross bar type for use in setting It is an object of the present invention, thereup connections between the various lines of an fore, to provide inatelephone system an improved 5 automatic telephone system, form of automatic switch of the cross bar type 5 It is well known that the method by which a which is of simple and economical and rugged connection is established from one line of a teleconstruction and which obviates the disadvanphone system to any desired second line in the tages of conventional switches of this type as system consists of routing a connectionby way pointed out above.

l of trailic concentration switches, and two or more VMore Specifically, it is an object of the invenl0 tandem connected impulse responsive numerical tion t0 provide an automatic Switch of the charswitches which operate automatically to select the acte-r noted Which may readily be substituted for desired line and to establish a connection thereto. any of the well-known forms of step-by-step Various types of numerical switches for performnumerical SWitClleS in an installed System and l ing the functions noted are known to the ern wherein there is insured positive engagement bel5 Perhaps the best known and most commonly used tween the contacts associated with the line incomswitch of this type isx the Srl-called Strowgcr ing to the switch and the contacts associated with switch employing a movable wiper mechanism any selected Outgoing line, the number 0f relays having two directions of movement. The complifor actuating the Various contact sets is reduced cated nature of this type of switchhas led to cont0 e minimum, and the COI1tr0l apparatus, Where- 20 siderable research in attempts to secure more simby a particular line OutgOng frOm the Switch iS ple and less expensive switches' capable of per- Selected, lS Simple in the eXtreme.

forming the same functions, one of the out.. The improved automaticswitch, as described in growths of this development is the so-called cross; n detail hereinafter. iS SllOWrl eS being embodied in bar type of switch, of which several modiiications all elltOmatiC telephone System 0f the general 25 have been devise@ one of the best known and character briefly described above and which commost. Successful forms 0f the cross bar Switch yet DIlSeS line Switches individual t0 Bach 0f 'the lines developed is that employlng Stationary conducincluded in the system, groups of iirst numerical tors 0r bars arranged in Sets leading t0 the lines OI intermediate Select/O1 SWl'lChBS t0 Which the line outgoing from the switch and wipers or contacts Switches are accessible, and groups 0f final nu- 3o connected to the incoming trunk line of the switch merical or connector switches which are accessible and arranged selectively to be brought into ento each of the intermediate selector switches. In gagement with the sets of bars, corresponding to general, the objects as set forth above are realized the various outgoing lines, by actuating means in in aeeoidanee with tile present invelltOIl by PrO- the form of relays. 'rnc method of selection of a vidins as the intermediate and nal numerical 35 particular line in the outgoing group of lines to switches automatic switches each of which comwhich the switch has access is accomplished by 'DI'lSeS a plurality ef gr011DS-0f C0r 1teCtS,eBeh grOllD control means for the wiper actuating relays, this being arranged 1n SetS lnellldlrlg One 0r more control moans functioning in responso to received individual contacts, each set ,beine mdlvidually 40 impulses transmitted from a calling substation to Connected t0 the une incommg t0 me SWltCh, 40

select a particular relay, following which the actuatmg means common to each grou? Pf con" selected relay is energized to establish a connecmots for moving the Same from (lne posmon to a' tion between the incoming trunk line to the switch secngtposlj(iigriildggpse con a s, e ggcegCfolletvgearfn individually connected to the lines outgoing from the switch actuating means common to each of a few countries, 1t has not been generally accepted m as a substitute for the Strowger type of Switch the second mentioned group of contacts for ov ing the same from one position to a second posibec-ws@ o? @81mm dlsadvaftages 1n regard to lts tion, and control means for selectively energizing Constructlonal and cfperatlonal features- AS an the actuating means in accordance with received 50 eaample of these dlsadvantages there may be impulses transmitted to the switch; the contacts Clted the feet that the Centrel means, whereby of the first-mentioned plurality of groups of condeSired Ones 0f the Wiper etlleting relays are tacts being so arranged relative to the contacts of selected, is of a complicated nature and the fact the second-mentioned plurality of groups ci conthat the connections. secured between the wipers tacts thatV when the contacts of one group of each 55 plurality of groups are moved to their respective second positions, the one or more individual contacts of a single set included in the moved group of the first-mentioned plurality ci groups engage the one or more individual contacts ci a single set included in the moved group of the secondmentioned plurality oi' groups.

More specifically, the actuating means for each group of contact sets comprises a single bar associated with the contacts of the corresponding group and adapted to be movedirom one position to a second position by a single operating magnet. In an arrangement for serving one hundred lines, ten vertical bars requiring ten operating magnets hereinafter designated as vertical magnets and ten horizontal bars requiring ten operating magnets hereinafter designated as horizontal magnets must be provided, each oi the vertical and horizontal bars being arranged simultaneously to actuate ten contact sets.

The control means included in the automatic switch comprises a single stepping switch of the rotary type having a normal position and a plurality of ofi-normal positions each of which corresponds to a group of' lines in the plurality of lines outgoing from the switch and a particular line in each group. More specifically, the stepping switch includes a plurality of sets of contacts, wipers individually associated with the contact sets, and a motor magnet for causing repeated operations of the switch, to select a desired group of lines and a particular line in the selected group. The motor magnet for vactuating the wipers of the switch is under the control of impulse responsive means comprising a line relay, and this means is arranged in different manners depending upon whether the switch is to be used as an intermediate selector unit or a nal selector unit. In the first-mentioned case, the control means operates in response to a predetermined` series of received impulses to cause the motor magnet to step the wipers of the stepping switch to a position corresponding to the selected group of outgoing lines,

following which the motor magnet is automatically conditioned to cause the wipers to continue to be stepped, thereby automatically to test the lines of this group until an idle line in the selected group is found. Following the selection of an idle line in the selected group, means operate to reenergize the motor magnet, thereby to restore the stepping switch to normal. When used as a iinal selector or connector unit, the control means associated with the stepping switch includes means for causing the wipers of the switch to be returned to normal at the conclusion of the first or tens series of received impulses and following the selection of a desired group of lines, following which the wipers are stepped in accordance with the impulses of the final or units series of received impulses at the rate of one step for each impulse until the wipers stand opposite the position corresponding to the particular called line in the selected group of lines. As will be brought out in greater detail hereinafter, the mechanism of the automatic switch as well as the control means associated therewith for procuring the form of operation briey described above is exceedingly simple .in arrangement and reliable in operation.

The novel features believed to be characteristc of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the speciiication taken in connection with the accompanying drawings, in which Figure 1 illustrates the general structural i'eatures of an automatic switch constructed in accordance with the present invention; Fig. 2 illustrates the details oi one Aoi' the horizontal magnets included in the switch oi.' Fig. 1; Fig. 8 illustrates the details oi' one of the vertical magnets included in the switch of Fig. 1; Figs. 4 to 8, inclusive, illustrate the three contact positions for the contact springs included in a contact spring assembly associated with the vertical magnet of Fig. 3 and the horizontal magnet of Fig. 4; and Figs. 7 and 8 illustrate a complete telephone system including automatic switches of the form shown in Fig. 1 used both as the intermediate and final selector units.

Referring now more particularly to Fig. 1 oi.' the drawings, the mechanical arrangement of an automatic switch constructed and arranged in accordance with the present invention is illustrated. As shown, the switch mechanism is adapted to be supported on shelves such, for example, as the shelves i3, I4, I5, I6 and i1 extending between and secured to side member il of a. frame I2. Mounted on each oi' the enumerated shelves is a horizontal magnet, those for the shelves mentioned being indicated at I8, I9,'

20, 2| and 22, respectively. Each of these horizontal magnets includes an armature upon which is mounted the horizontal member or bar for actuating the group of contact sets corresponding tothe particular magnet. Thus, the magnets i 8 to 22, inclusive, include, respectively, armatures 23, 24, 25, 26 and 21, upon which are mounted, respectively, the actuating bars 28, 29, 30, 3| and 32. Each of these bars is guided in its movement in the vertical plane by guide lugs mounted on the shelf carrying the associated magnet in a manner identical with that shown for the bar 28. The ends of the last-mentioned bar ride in slots provided in the upright portions of lugs 33 and 34, mounted at either end of the shelf I3. Each of the horizontal bars 2.8 to 32, inclusive, in cooperation with its respective associated horizontal magnet comprises means for actuating the contacts of an associated group of contact sets from their respective normal positions to their respective oir-normal positions. Thus, the bar 28 has associated therewith a group of contact sets, four of which are indicated at 35, 36, 31 and 38. Each of these contact sets includes one or more individual contacts. If the size of the switch requires that a large number of contact sets be placed under the control of each horizontal bar, two horizontal magnets may be required for actuating each bar, one magnet being positioned at each end of eachbar. It will readily be apparent how such additional magnets could be embodied in the structure shown. It will further be apparent that the two magnets associated with each bar could have their respective windings connected in multiple for simultaneous energization.

Mounted on the lower shelf I1 is a group of vertical magnets. five of which are indicated at 3,9, 40, 4I, 42 and 43, which individually include, in the order named, armatures 44, 45, 46, 41 and 48. Each of these armatures is arranged to actuate a vertical bar associated with one group of vertical contact sets and guided in its movement by a pair of brackets projecting outwardly from the shelves I3 and I6. These brackets,

comprising the pair for guiding the bar associ- -responding group of vertical contact sets.

ated with the magnet 39 in its movement, are shown at 64 and 65. The bars associated with the armatures noted are indicated at 49, 50, l., 52 and 53, respectively, and each thereof carries a plurality of projecting arms individually associatedwith one of the contact sets of the cor- Thus, the bar 49, which is under the control of the magnet 39, carries a plurality of arms, five of which are indicated at 54, 55, 56, 51 and 58, each of which projects inwardly and sidewise from the bar 49 so that, when the bar is pulled downward by the armature 44, all of the contacts included in the associated group of contact sets are moved from their respective normal positions to their respective oil-normal positions. The Contact sets shown in association with the arms 54 to 58, inclusive, of the vertical bar 49 are indicated at 59, 60, 6l, 62 and 63, respectively. Each of the contact sets includes one or more individual contacts.

It will be understood that, when a switch of the above-described form, designed to have access to one hundred outgoing lines, is selectively operated to connect a line incoming thereto to any one of the outgoing lines, one hundred contact sets will be required in each of the plurality of groups of contact sets associated respectively with the horizontal and the vertical bars. This necessarily means that ten vertical bars will be required, each arranged to actuate a group of ten contact sets, and ten horizontal bars will be required. each similarly arranged to actuate a group of ten contactsets. It will further be apparent that the conductors of the incoming line including the trunk and test conductors thereof must necessarily be multipled between the corresponding contacts of all of the contact sets of one plurality of groups of contact sets. Thus, if the incoming line is connected to the plurality of groups of contact sets associated with the horizontal bars, the conductors thereof must necessarily terminate at each of the contact sets actuated by each of these bars. The outgoing lines, on the other hand, terminate only at individual ones of the opposite contact sets or, in the assumed case, one line will terminate at each of the contact sets 59, 60, 6l, 62, 63, etc. associated with the vertical bars.

In order selectively to energize the various vertical and horizontal magnets, there may be provided control means comprising a stepping switch of the rotary type diagrammatically illustrated at 66, which includes two contact sets 61 and 58. The individual contacts of the set 61 are connected to one terminal of a corresponding horizontal magnet, HMI, HMZ, etc., and the individual contacts of the set 68 terminate at one terminal of a corresponding vertical magnet, VMI, VM2, etc., thereby to permit the various magnets to be selectively energized. While this control means is described in greater detail hereinafter, it is mentioned at this point in order to facilitate an understanding of the manner in which the switch mechanism operates.

Referring now more particularly to Fig. 2 of the drawings, there are illustrated the details of one of the horizontal magnets such, for example, as the magnet 22 shown in Fig. 1 and of one of the spring assemblies associated with the corresponding horizontal bar 32 and the vertical bar 49. This magnet includes a magnetic core comprising a central leg 69 having a winding 10 wound thereon, a heel piece 1l, a side piece 12, and an armature 21. The various contact spring assemblies, which individually comprise one contact of each of a pair of associated horizontal and vertical contact sets, are carried by an extension from the i'side piece 12. Thus, one of the assemblies in t e pair of sets associated with the horizontal bar 32 and the vertical bar 49 comprises springs 14 and 15, mounted on the side piece 12 and insulated from each other by an insulating member 16, and from the assembly `screws by additional insulating members 11 as shown. The armature 21 is pivoted at 19 and carries the cross bar 32 for actuating the group of springs including the contact set of which the spring 15 is a part. This cross bar is insulated from the spring 15 by an insulating member 80. Each of the other contact springs associated with each of the horizontal bars is similarly insulated from its associated bar. The upper associated set of contact springs comprising the set, of which the spring 14 forms a part. is under the control of the arm 58 projecting from the vertical bar 49. This arm is insulated from the associated set of contact springs by an insulating member 8|. Each of the other contact springs'associated with each vertical bar is similarly insulated from the corresponding bar.

Referring now to Fig. 3, there is illustrated the vertical magnet 39 for actuating the Vertical bar 49 associated with the contact set including the contact spring 14. This magnet comprises a magnetic core having a central leg 94 having a Winding 85 thereon, a heel piece 82, a side piece 83, and an armature 44. This armature is pivoted at 81 and is arranged to actuate its associated vertical bar 49 through a toggle member 88. As will be pointed out in greater detail hereinafter, the number of springs included in the assembly of each of the contact sets associated with a vertical bar is dependent upon whether the automatic switch is to be used as an intermediate or final selector unit. If used as an intermediate selector unit, three springs are, as shown, included in each third spring assembly, the third spring 16 being utilized for testing the condition of the outgoing line terminating at the corresponding set of contacts. The remaining two spring assemblies included in each associated pair of Contact sets comprise only two contact springs, corresponding to the springs 14 and 15 of the assembly shown. In the event the switch is to be used as a final selector unit, only the contact springs, corresponding to the upper and lower springs of the assembly shown, will be incorporated in each spring assembly, the central spring corresponding to the spring 16 being omitted. If required, each of the horizontal and vertical magnets may be provided with additional armatures or contact springs for the purpose of controlling the operation of `the switch. Any conventional manner of embodying such additional springs in the magnet structure may be employed.

In the operation of the switch as thus far described, and when one of the vertical magnets such, for example, as the magnet 39 is selected and energized, the bar 49 carried by the armature 44 thereof is moved downward to actuate the contacts of all of the contact springs associated with this bar and included in the sets 59, 60, 6I, 62 and 63, from their respective normal positions to their respective off-normal positions. This operation corresponds to the selection of a particular group of outgoing lines and, as will be pointed out in greater detail hereinafter, the particular vertical magnet which is energized corresponds to a particular number of impulses in a series of impulses received by the switch. In the event the switch is used as an intermediate selector unit, this operation causes the contacts on the springs, corresponding to the springs 14 and 10 and included in all of the sets associated with the vertical bar 49, to make contact, thereby to mark the condition of all of the lines of the selected group in the bank contacts of the rotary stepping switch, whereby the lines in the selected group may be tested. In the event the switch is to be used as a final selector or connector unit, no such testing is required, and this explains the reason why only two contact springs are necessary in each spring assembly embodied in this form of switch. Following the energization of one of the vertical magnets, a selected one of the horizontal magnets such, for example, as the magnet 22, is energized, thereby to actuate all of the contacts in the sets associated with the horizontal bar 32 from their respective normal positions to their respective oil-normal positions and to complete a connection between'the line incoming to the switch and a particular one of the lines in the selected group of lines outgoing from the switch. Thus, with the vertical magnet 39 and the horizontal magnet 22 energized, only the contacts included in the set of vertical contacts 63 will be in engagement with the contacts of the associated horizontal contact set, the remaining contact sets being disengaged due to the deenergized condition of the other vertical and horizontal magnets.

An understanding of the mode of operation just described is facilitated by considering the sequence of contact spring movements illustrated in Figs. 4, 5 and 6, for the spring assembly 14, 15, 16 associated with the horizontal magnet 22 and the vertical magnet 39. Normally, and with the two magnets noted deenergized, the springs 14, 15 and 16 are in the open contact positions illustrated in Fig. 4. With only the vertical magnet 39 energized, the spring 14 is pushed down so that the contacts on the springs 14 and 16 make contact, but the contacts between the springs 'i4 and 15 remain disengaged, as shown in Fig. 5. This permits the testing operations noted above to\be performed. Thereafter, and when the horizontal magnet 22 is energized, the lower spring 15 is pushed up so that the contact of this spring engages the contact of the spring 14, as shown in Fig. 6. Thus, it will be seen that, with one horizontal magnet energized and one vertical magnet energized, the incoming line to the switch is connected only to a particular one of the outgoing lines.

Referring now more particularly to Figs. 7 and 8, considered together, there is illustrated a telephone system wherein automatic switches of the form just described are used as the impulse responsive, intermediate and nal selector switches. In general, the system comprises a plurality of telephones or subscribers substations, two of which are shown at A and B, adapted to be interconnected by means including their respective subscribers lines 00 and |00 and switch trains including the aforementioned intermediate and nal selector switches. These switch trains, when established, may individually comprise the usual line switch associated with each subscribers line, an intermediate selector switch accessible to the line switch associated with the subscribers line, and a final selector switch accessible to the operated selector switch and having bank contacts in which the called subscribers line terminates. Thus, in the system shown, the line 00 terminates at a line switch |03, which switch has access to a group of selector switches, one oi which is indicated generally at |04. 'I'he latter switch in turn has access to groups of flnal selector or connector switches, each connector switch of each group having its bank contacts multipled to the bank contacts of the other switches in the same group and connected to serve a corresponding group oi' subscribers lines Y included in the system. Thus, the selector, switch |04 has access to connector switches, one oi' which is indicated generally at |05, in the bank contact sets of which the subscribers line |00 terminates. It is well known that by this general arrangement any subscriber may by proper manipulation o! the impulsing device at his substation establish a connectionbetween his line and any other idle subscribers line in the system.

Each of the line switches included in the system, such, for example, as the line switch |03, may be of any desired commercial construction,

although preferably is oi' the well-known rotary type having three levels of bank contacts, wipers corresponding to the three levels, a ratchet and pawl mechanism for driving the wipers, an operating magnet for actuating the ratchet and pawl mechanism and control means whereby the operating magnet is energized to operate buzzer fashion when a call is initiated on the line associated with the corresponding line switch and is deenergized when the wipers are rotated into engagement with a set of contacts corresponding to the first idle intermediate selector switch available.

Neglecting for the present the details of the intermediate and final selector switches |04 and |05, respectively, and the control means respectively included therein, the system as described above is entirely conventional in form and its operation is well understood in the art. In brief, when a subscriber such, for example, as the subscriber at the telephone A initiates a call over the line |00 to a second subscriber-s telephone such, for example, as the telephone B by lifting his receiver from its hook, the line switch |03 associated with the calling subscribers line operates to select an idle intermediate selector switch and to condition the same to be responsive to impulses transmit-ted from the impulsing device at the telephone A. As noted above, each of the intermediate selector switches has access to one or more final selector switches at which any subscribers line of the system terminates. Thus, if the intermediate selector switch |04, for example, is seized by the line switch |03, it operates in response to the dialing of the rst digit at the substationA to select a group of trunk lines extending to the group of final selector switches at which the called line |00 terminates. Following this, the seized intermediate selector switch |04 automatically selects a trunk line leading to an idle nal selector switch in the selected group of switches and connects the calling subscribers line |00 through to seize this idle ilnal selector switch. Thereafter, and in response to the dialing of the second digit, the seized nal selector switch selects the group of lines in which the called subscribers line |00 is included. With the switch train in this condition, and when the inal or third digit is dialed, the seized final selector switch selects the par- 'ticular called line in the selected group of lines 75 and, if this line is idle, establishes a connection between the calling and called lines when the called telephone B is answered.

The system conventionally includesmeans whereby ringing current and ring-back tone current are automatically transmitted, respectively, to the substations of the called and calling parties in case the called line is idle and upon the nal selector switch seizing the called line. Also, in accordance with conventional practice, means are provided whereby, in the event the called line is found busy, the calling line is not connected thereto and busy tone current is transmitted back over the established loop to the calling party to indicate the busy condition of the called line. As will be pointed out in detail hereinafter the arrangement is such that the switch train utilized in establishingthe connection is released only when the connection is cleared out at the calling party's substation, the entire switch train being held operated when the called party is the ilrst to hang up.

Each of the intermediate and final selector switches preferably embodies the features of the improved automatic switch illustrated in Figs. 1 to 6, inclusive, although it is noted that the system may only partially comprise switches of this form, the remaining automatic switches being of any well-known step-by-step type wherein impulse responsive means are utilized to control the operation thereof. The selector switches |04 and |05 are, however, of the form illustrated in the above noted figures and the mechanical con-` structions of the two switches are identical with the exception that the nal selector switch |05 includes only two springs in each contact spring assembly whereas the switch |04 includes three contact springs in the third contact spring assembly included in each associated pair .of conthe vertical magnet 240.

tact sets. Two additional contact spring pairs are associated with each of the horizontal and vertical magnets included in each of the intermediate selector switches and` one additional spring pair is associated with each of the horizontal and vertical magnets embodied in each of the final selector switches, these additional springs being used for control purposes in the manner described hereinafter. The switch |04 has access, over one hundred outgoing trunk lines, one of which is shown at |09', to each of one hundred final selector switches and, similarly, each of the nal selector switches has access to one hundred subscribers `lines terminating at the contact springs associated with the vertical bars of the switch. In view of the previous description, it will be understood that the springs 263 to 265, inclusive, comprise one contact set forminga part of a group of ten similar contact sets under the control of the horizontal actuating b 'ar associated with the horizontal magnet 260 and that the contact set comprising the springs 24| to 244, inclusive, is one of a group of ten similar contact sets under the control of the vertical actuating bar associated with Similarly, the horizontal magnet 380 of the nal selector switch |05, in cooperation with its associated horizontal bar, controls a group of ten contact spring sets including the set of springs 362, 383 and 384, and the vertical magnet 390 in cooperation with its associated vertical bar controls a group of contact sets including the contact springs 30|, 392 and 393. It will further be understood that the contact springs 243, 244 and 265 comprise one contact spring assembly and, similarly, that the associated springs 242, 264 and 24|, 263 comprise the two other assemblies of the associated vertical and horizontal contact sets.

The circuit arrangement of the control means included in the intermediate selector switch |04 is necessarily quite different from that of the control means included in the switch |05. This difference is necessitated by the fact that the switch |04 need only operate in response to one series of received impulses to select a particular group of lines, following which it must operate automatically to select an idle line in the selected group of lines, whereas the switch |05 must be responsive to two series of received impulses to select both the desired group of lines and the particular called line in the selected group. This control means for the switch |04 comprises a stepping switch of the rotary type including three sets of contacts 2|4, 2|5 and 2|6, wipers 201, 208 and 209 for respectively engaging the enumerated sets of contacts, a ratchet and pawl mechanism, not shown, for actuating the wipers 201 to 209, inclusive, a rotary magnet 205 for actuating the ratchet and pawl mechanism, and oil-normal springs |60 for causing the stepping switch to be returned to normal when a connection utilizing the selector switch |04 is released. The control means for the automatic switch indicated also includes a plurality of relays 200, 2|0, 220, 230, and 250, their control and controlled circuits, arranged to operate as described in detail hereinafter to insure the automatic selection of an idle final selector switch in a selected group of such switches in the manner briefly referred to above.

The control means embodied in the final selector switch |05 similarly includes a stepping switch of the rotary type comprising two sets of contacts 3|1' and 3|8, wipers 3|5 and 316 for respectively engaging the two sets of contacts named, a ratchet and pawl mechanism, not shown, for actuating these wipers, a motor magnet 301 for driving the ratchet and pawl mechanism and off-normal springs 300 for causing the magnet 301 to return the stepping switch to normal during the release of a connection in which the automatic switch |05 is involved. This control means also includes a plurality of relays 300, 3|0, 320, 330, 340, 350, 360, and 310, the control and controlled circuits, which relays in cooperation with the stepping switch are operable in the manner set forth in detail hereinafter to cause the switch |05 to perform the line selecting functions briefly described above. The switch |05 also has associated therewith ringing apparatus, not shown, for transmitting ringing current to a called subscribers line and ring-back tone current to a calling subscribers line, and a generator, not shown, for transmitting busy tone current to a calling subscribers line in the even a particular called line is found busy.

Considering now the detailed operati-on of the intermediate selector switch |04 during the above described sequence of operations, when this switch is seized by the line switch |03, a circuit is completed for energizing the line relay 200, which circuit extends from ground at the upper winding of the relay by way of this winding, to the conductor |21, the armature 252, the trunk conductor |01, the line'switch |03, the line conductor I0|, the bridge across the line |00 at the calling substation A, the upper line conductor |02, the line switch |03, the trunk conductor |06, the armature 25|, the conductor |26, and the lower winding of the relay 200 to battery. The

line relay 200 operates in response to its energization over the above-traced circuit to complete, at its armature 202 and associatedupper contact 203, a circuit for energizing the slow-torelease hold relay 2|0,this circuit extending from ground at the restored armature 255, by way of the conductor |20, the armature 202, the contact.- 203, and through the winding of the hold relay 2|0 to battery. At its armature 20|, the line relay 200 opens a point in the circuit for energizing the slow-to-release relay 220.

- The hold relay 2| 0, upon operating, applies, at its armature 2| ground to the control conductor |08, thereby to hold the line switch |03 operated and to maintain the calling line |00 marked as busy in the banks of the final selector switches. The application of ground to this conductor completes an obvious circuit for holding the lower winding of the polarized relay 250 energized, thereby .to render this relay exceedingly fast to operate when its upper winding is energized. At its armature 2|2, the hold relay 2|0, upon operating, prepares a point in the circuit ior energizing the relay 220. At its armature 2|3, the relay 2|0 prepares a circuit for energizing the motor magnet 205 of the rotary stepping switch. At its armature 2|3', the holdv relay 2|0 opens a point in a circuit, traced hereinafter, for causing the motor magnet 205 to return the wipers 201 to 209, inclusive, to their respective normal positions following the selection of a trunk line extending to an idle nal selector switch in a selected group. With the relays 200 and 2|0 of the switch |04 operated, the control means included in this switch is conditioned to be responsive to the series oi' impulses comprising the first digit dialed at the calling substation A.

At the beginning of the first impulse of this digit, when the previously traced circuit for energizing the line relay 200 is interrupted at the impulsing device of the calling substation, this relay restores to complete, at its armature 202 and associated contact 204, the previously prepared circuit for energizing the motor magnet 205, this circuit extending from ground on the restored armature 255 by way of the conductor |20. the armature 202 and associated contact 204, the armature 2| 3, the conductor ||9 and the winding of the magnet 205 to battery. Simultaneously, the previously prepared circuit for energizing the relay. 220 is completed at the armature 20| of the line relay200 and the rstmentioned relay, namely, the relay 220, operates to complete, at its armature 22| and the associated contact 222, an obvious circuit for energizing the slow-to-release relay 230. 'Ihe relay 22, upon operating, also opens, at its armature 224, a point in the circuit, traced hereinafter, for energizing the upper winding of the polarized relay 250. When the relay 230 pulls up; it prepares, at its amature 232, a circuit for energizing any one oi' the ten vertical magnets of the switch |04 selected by the rotary stepping switch, this circuit being held open at the operated armature 22| until the selection is made. At its armature 23|, the relay 230, upon operating, opens a point in an alternative circuit, traced hereinafter, for energizing the winding of the motor magnet 205.

At the beginning of the first pulse of the first dialed digit, when the line relay 200 restores, the previously traced circuit for energizing the motor magnet 205 is completed at the armature 202, and this magnet in cooperation with the associated ratchet and pawl mechanism, not shown, steps the wipers 201 to 200, inclusive, one step or into engagement with the respective first contacts of the three contact sets 2|4, 2|5 and 2| 6. Simultaneously the off-normal springs |60 are closed to prepare a circuit for causing the motor magnet to restore the` wipers to their respective normal positions'. During each succeeding impulse of the series of impulses comprising the first digit, the line relay 200 alternately operates and restores to cause the motor magnet 205 in cooperation with its associated ratchet and pawl mechanism to step the wipers 201 to 209, inclusive. at the rate of one step for each impulse r'eceived by the automatic switch. During such impulsing, the relays 2|0, 220 and 230, by

.virtue of their slow-to-release characteristics,

remain operated.

Since the outgoing line |00 terminates at a set of contacts under the control of the vertical magnet 240 corresponding to the third contact of the contact set 2|4, the first digit dialed at the calling substation will necessarily comprise three impulses, so that, at the conclusion of this digit, the wipers 201 to 209, inclusive, stand in their respective third positions with the wiper 201 in engagement with the contact corresponding to the vertical magnet 240. Shortly following the end of the rst digit, and with the line relay 200 in its operated position such that the circuit for energizing the relay 220 is interrupted at the armature 20|, the last mentioned relay restores to prepare, at its armature 224, a point in the circuit for energizing the upper winding of the polarized relay 250. At its armature 22| and associated lower contact 223, the relay 220, upon restoring, completes a circuit for energizing the vertical magnet 240, this circuit extending from ground on the armature noted, by way of the contact 223, the operated armature 232, the conductor 2|, the wiper 201 and its associated third contact, the conductor 3, and the winding of the vertical magnet 240 to battery. This vertical magnet, upon operating, completes, at its armature 245, a locking circuit extending by way of the conductor ||4 to ground on the control conductor |08 for holding itself operated independently of the rotary stepping switch. At its armature 246, the magnet 240-prepares a circuit, traced hereinafter, for energizing the motor magnet 205, by way of its self-interrupting cony tacts 206. 'I'he magnet 240 in cooperation with its associated vertical bar also actuates each of the contact springs of all of the contact sets included in the group of ten sets associated therewith from their respective normal positions to their respective off-normal positions. Thus, the contact springs 24|, 242 and 243 are pulled down so that the spring 243 connected to the control conductor of the trunk line leading to the final selector switch |05 is connected to the spring 244 leading by way of the test conductor 2 to the rst contact in the contact level 2|5 associated with the wiper 208. It will be understood that each of the remaining nine lines in the group including the line |09', and terminating at the contact sets in the same'group as the set 24|, 242, 243 have their respective control conductors connected by way of a test conductor corresponding to the conductor ||2, vto a corresponding contact of the contact level 2| 5. Thus, the switch |04 is automatically conditioned to test the trunks in the selected group of trunks until an idle one thereof is found. As will be seen from a consideration of the final selector switch |05,

if any particular final selector switch in the selected group is idle, battery is present on'the control conductor corresponding to the conductor II I, whereas if it is busy ground is present on this conductor. Thus, when the switch I 05 is idle, the armature 3| 2 of the hold relay 3|0 is restored and battery is present on the control conductor I I If, on the other hand, this switch is busy, the armature 3I2 is operated andground is present on the conductor III.

The testing of the lines in the selected group is initiated when the slow-to-release relay 230 falls back shortly after the end of the ilrst dialed digit and following the restoration of the relay 220, When this occurs, the original circuit for energizing the vertical magnet 240 is interrupted at the armature 232 and a circuit is completed, at-the armature 23|, for energizing the motor magnet 20,5, by way of its self-interrupting contacts 206, this latter circuit extending from ground on the control conductor |08, by Way of the conductor II4, the armature 246, the conductor II6, the armature 253 and associated contact 254, the conductor I|5, the armature 23|, the conductor H8, and through the self-interrupting vcontacts 206 and the Winding of the motor magnet 205 to battery. It will be observed that the Wipers 201 to 209, inclusive, of the stepping switch are not restored to normal but start testing from the position which they occupy at the conclusion of the first digit. Thus, in the case under consideration, the wiper 208 stands in its third position and tests successively the lines corresponding to the contacts including and following the third contact of the contact set 2I5. In the event the trunk line leading to the third nal selector switch of the selected group is idle, the wiper temporarily remains in this position, a circuit being cornpleted at the contacts 243 and 244 immediately the vertical magnet 240 operates for causing the immediate operation of the polarized relay 250 before the motor magnet 205 has had suilcient time in which to operate in response to its energization over the above traced circuit. In the case under consideration, however, it is assumed that the iinal selector switches in the selected group and corresponding to the fourth to tenth contacts inclusive, of the contact set 2|5 are busy and that the switch I 05 corresponding to the rst Contact of the set 2I5 is the iirst available idle nal selector switch. Hence, the motor magnet starts to operate buzzer fashion and in cooperation with its associated ratchet and pawl mechanism drives the wipers 201 to 209, inclusive, over the enumerated contacts until the Wiper 208 engages the rst contact of the contact set 2I5, whereupon a circuit is completed for energizing the upper winding of the polarized relay 250, this circuit extending from ground on the control conductor |08 by way of the conductor |28, the upper winding of the relay 250; the conductor |29, the restored armature 251, the restored armature 224, the conductor |23, the wiper 208, the first contact of the contact set 2|5, and the conductor ||2 to battery on the control conductor III of the line |09. The polarized relay 250 immediately operates and interrupts, at its armature 253 and associated contact 254, the previously traced operating circuit for the motor magnet 205. At its armature 258, the relay 250 completes a circuit for energizing the winding of the horizontal magnet 260, this circuit extending from ground by way of the armatures, corresponding to the armature 26 I, associated with the other horizontal magnets and indicated bythe dash line 26|', the armature 26|, the conductor |30. the armature 258, the conductor |24, the wiper 200, and its associated nrst contact, the conductor I20,'and through the winding of the magnet 260 to battery. Atits armature 261, the relay 250 interrupts the previously traced circuit for energizing its upper -winding but it remains operated by virtue of the energized condition of its lower winding. At its armature 256, this relay Iurt'her interrupts the operating circuit of the hold relay 2|0 and opens a point in the original circuit for energizing the motor magnet 2 05. At its armature 253, the relay 250 prepares a third circuit for energizing the motor magnet 205 to restore the wipers 201 to 209, inclusive, to normal, this latter circuit being held open at the armature 2| 3 until the hold relay 2 I0 restores.

The horizontal magnet 260, upon being energized in the above described manner, operates to complete, at its armature 262, an obvious holding circuit for itself and to interrupt, at its armature 26 I, a common point in the circuits for energizing the other horizontal magnets. At its contact springs 263, 264, and 265, the magnet 260 connects the trunk line |06 incoming to the switch |04 to the selected outgoing trunk line |09. The last mentioned operation extends the loop from the calling subscribers substation A to the seized nal selector switch |05 and results in the energization of the line relay 300 in the latter switch over a circuit including this loop. This line relay, upon operating, completes, at its armature 30|; an obvious circuit for energizing vthe hold relay 3I0, which relay operates to apply, at the armature 3 I2 and associated contact 3 I4, ground to the control conductor III. This ground is extended through the operated contact springs 243 and 265 to the control conductor |08, thereby to maintain energized the operated horizontal and vertical magnets 260 and 240, respectively, independently of the control means included in the intermediate selector switch |04.

As a further consequence of the operation of the polarized relay 250 in the switch |04, the operating circuit for the line relay 200 is interrupted at the armatures and 252. This line relay, upon falling back, at its armature 202 and associated contact 203, interrupts a further point in the previously traced operating circuit for the hold relay 2|0. Restoration of the line relay 200 also causes the sequential operation of the relays 220 and 230, but these operations are without eiect at this time.

When the hold relay 2|0 restores, shortly after the application of ground to the conductor |08 at the armature 3I2 of the hold relay 3|0, it removes, at'its armature 2II, multiple ground from the control conductor |08. At its armature 2I3, the hold relay 2 I0 completes a circuit for again energizing the motor magnet 205, this circuit extending from ground on the control conductor |08, by way of the conductor II4, the operated armature 246, the conductor I I6, the operated armature 253 and its associated contact 255, the conductor |25, the armature 2I3, the conductor |I1, the offnormal springs |60, th econductor IIB, and through the self-interrupting contacts 206 and the Winding of the motor magnet 205 to battery. Restoratiton of the hold relay 2|0 results in the interruption, at the armature 2|2, of the circuit over which the relay 220 was reoperated, which relay restores after an interval to cause the restoration of the relay 230, the restoration of the relay 220, due to its slow-to-release characteristic, being subsequent to the return of the wipers 201 to 299, inclusive, .to normal or home positions in the manner explained below.

The motor magnet 205, upon being energized over the above traced circuit, operates buzzer fashion and in cooperation with its associated ratchet and pawl mechanism drives the wipers 201 to 209, inclusive, to their respective normal or home positions, at which time the oil-normal springs |60 open to interrupt the operating circuit of this magnet. Thus. the rotary stepping switch is returned to normal immediately following the seizure of an idle final selector switch in the selected group. It is noted here that the energization of the remaining horizontal magnets during the restoration of the stepping switch to normal is prevented by the operation of the armature 25| before the restoring operation occurs. The polarized relay 250 upon operating prepares a circuit for each of these magnets, but these circuits include a common portion 26 I comprising the series connected armatures, corresponding to and including the armature 20|. Hence, when any one of the horizontal magnets is energized the energizing circuit for each of the other horizontal magnets is opened independently of the relay 250. With the system in this condition, it will be seen that the connection has been extended. to the seized iinal selector switch, that'only the relay 250 and the magnets 240 and 260 of the switch |04 are operated, and that the rotary stepping switch in the intermediate selector switch |04 is in its normal position ready for further use.

The operation of the line relay 300 and the hold relay 3|0 in the seized final selector switch |05 conditions this switch to be responsive to impulses comprising the two nal digits dialed at the calling substation A. Thus, the hold relay 3|0, upon operating, applies, at its armature 3| ground to the conductor |43, to prepare holding circuits for all of the vertical and horizontal magnets included in the switch and for the ring cut-olf relay 360 and the relay 310. At its armature 3l5, the hold relay prepares a circuit for energizing the slow-to-release relay 320, this circuit being held open at the armature 30| and associated contact 302 of the operated line relay 300. At its armature 3| 6, the relay 3|0 opens a point in the circuit for energizing the magnet 301 by way of the off-normal springs 309 and, at its armature 3 I1 it prepares an impulsing circuit for energizing this magnet independently of the springs 309.

At the beginning of the rst impulse of the second digit dialed at the calling substation, the line relay 300 restores, to complete, at its armature 30| and associated contact 302, the abovementioned circuit for energizing the relay 320 causing this relay to operate and complete, at its armature 32| and associated contact 323, a circuit for energizing the slow-to-release relay 330. The last-mentioned relay, upon operating, completes, at its armature 336 an obvious circuit for energizing the lower winding of the relay 340. Operation of the armature 335 of the relay 330 results in the preparation of a circuit, traced hereinafter, for energizing a selected one oi' the vertical magnets embodied in the switch. At its armature 331, the relay 330 opens a point in a circuit, traced hereinafter, f or causing the motor magnet 301 to'restore the wipers 3|5' and 3|5' to normal following the seizure of the called line.

When the lower winding of the relay 340 is energized in the above-described manner, this relay operates to complete, at the X contacts assoanni? ciated with the amature 344, a path for shortcircuiting its upper winding, this path extending from ground on'the control conductor by way'of the conductor IBI, the armature 344, the said upper winding, the armature 345, and back to ground at the armature 330. The remaining armatures 34| and 345 remain in their respective restored positions until such 'time as the above-noted short circuit around the upper winding of the relay 340 is interrupted' to permit the two windings of the relay to be energized in series.

Returning again to the operations which occur atA th'e beginning of the first impulse of the second digit, when the relay 300 restores, a circuit is completed for energizing the motor magnet 301, this circuit extending from ground on the armature 304, by way of the contact 305, vthe armature 3|1, the conductor |49 and through the winding of the motor magnet 301 to battery. The magnet 301, thereupon and in conjunction with its associated ratchet and pawl mechanism, drives the wipers 3|5' and 3|6 into engagement with the first contacts of their respective associated contact sets. When the wipers 3|5 and 3|6 of the stepping switch take this first step, the oil?- normal springs 309 are closed, further to prepare the circuit for-causing the motor magnet 301 to restore these wipers to normal. The motor magnet 301 is alternately energized and de-energized in accordance with the impulses of the second digit to step the wipers 3|5' and 3|0 over their respective associated contact sets at the rate of one contact for each impulse. In the case under consideration, wherein the called line |00 is in a group corresponding to the second contact of the contact set 3|1', the second digit will necessarily comprise two impulses, so that, at the conclusion of the digit, the wipers 3|5' and 3|6' stand in engagement with their respective associated second contacts. It will be understood that the relays 3|0, 320, and 330, due to their slow-to-release characteristics, remain operated during such impulsing.

At the conclusion of the second digit, the line relay 300 remains energized for a suiilcient period of time to permit the relay 320 to restore. When this occurs, a circuit is completed for energizing the vertical magnet 390 corresponding to the impulses comprising the digit dialed, this circuit extending from ground on the restored armature 32| by way of the contact 3.22, the operated armature 335, the restored armature 34|, the contact 342, the conductor |45, the wiper 3|5 and its associated second contact, the conductor |59, and through the winding of the magnet 390 to battery. This magnet immediately operates its armatures to complete, at the armature 394, a locking circuit extending from ground on the conductor |43 for holding itself operated. 'Ihe magnet 390 in cooperation with its associated vertical bar also operates all of the contact springs in the group of contact spring setscomprising the set of springs 39|, 392, and 393 from their respective normal positions to their respective off-normal positions.

It will be observed that, simultaneously with the completion of the above-traced circuit for energizing the magnet 390, the operating circuit for the relay 330 is interrupted at the armature 32| and its associated contact 323. I'his relay restores shortly after the vertical magnet 390 operates to interrupt, at its armature '335, the abovetraced original circuit for energizing the vertical magnet noted. As a further consequence of the restoration of the relay 330, a circuit is completed at'the armature 331 for energizing the motor magnet 301, to cause the wipers 3| 5' a-nd 3|6 to be returned to their respective normal positions, this circuit extending from ground on the operated armature 304, by way of the contact 305, the restored armature 331, the conductor |48, the closed off-normal springs 309, and through the self-interrupting contacts 303 and the winding of the magnet 301 to battery. The motor magnet 301 thereupon operates buzzer fashion and, in conjunction with its associated ratchet and pawl mechanism, drives the wipers 3|5' and 3|6 until they occupy their respective normal positions, at which time the off-normal springs 309 are opened to interrupt the circuit of the magnet 301. v

Simultaneously with the completion of the last-mentioned circuit for energizing the motor magnet 301, the previously traced short circuit for the upper winding of the relay 340 is interrupted at the armature 336, thereby causing the two windings of the relay 340 to be energized in series. The relay 340, thereupon, fully operates to interrupt at its armature 345 a further point in the short-circuiting path for its upper winding and to prepare, at its armature 34| and associated contact 343, a circuit traced hereinafter for energizing a selected one of the horizontal magnets embodied in the switch. Thus, the final selector switch |05 is conditioned to be responsive to the impulses comprising the third or units digit dialed at the calling subscribers substation A.

At the beginning of the first impulse of the third digit, when the line relay 300 again restores, the relay 320 reoperates, and the circuit for energizing the motor magnet 301 independently of its self-interrupting contacts 303 is again completed at the armature 304. It is noted here that both the relays 320 and 330 reoperate at the beginning of the third digit and that the latter relay prepares, at its armature 335, a further point in the above-mentioned circuit ior energizing a selected one of the horizontal magnets. When the motor magnet 301 is energized at the beginning of the iirst pulse,

, it causes the wipers 3I5' and 3|6' to be stepped into engagement with their respective associated iirst contacts and again closes the olf-normal springs 309. The wipers 3|5 and 3|6' are thereafter stepped in accordance with the succeeding impulses comprising the third digit at the rate of one point per impulse. In the present instance, Wherein 'the horizontal magnet 380 must necessarily be energized in order to complete the connection to the desired called line and this magnet is associated with the third contact of the contact set 3|8, the units digit will comprise three impulses so that, at the conclusion thereof, the wipers 3|5' and 3|6' stand on their respective associated third contacts. With the wiper 3|6 in this position, and when the relay 320 restores shortly following the end of the digit, a circuit is completed for energizing the selected horizontal magnet 380, this circuit extending from ground on the armature 32|, by Way of the contact 322, the operated armature 335, the operated armature 34| and its associated contact 343, the armature 355, the conductor |46, the armature 312, the conductor |41, the wiper 3IB and its associated third contact, the conductor |38, and through the winding of the magnet 380 to battery. The horizontal magnet 380, when energized over the above-traced circuit,

operates its amature 33| to complete a locking circuit for itself extending from ground on the conductor |43 and by way of thev conductor |55. This magnet, in cooperation with its associated horizontal bar, also operates all of the contact springs in the group of contact spring sets, including the set ot springs 382, 333 and 334, from their respective normal positions to their respective ofi-normal positions, whereby the contacts of theA enumerated springs engage the respective contacts of the operated springs 33| to 333, inclusive, thereby to complete a connection between the conductors |33, |34 and |40 of the line incoming to the switch and the conductors |35, |36 and |31, respectively, of the called line.

Shortly after the horizontal magnet 380 is energized, and when the slow-to-release relay 330 falls back, the previously traced circuit for energizing the motor' magnet 301 by way of the oit-normal springs 309 and the self-interrupting contacts 303 is again completed, thus causing the motor magnet 301 in cooperation with its associated ratchet and pawl mechanism to drive the wipers 3|5' and 3|6' until they stand in their respective normal positions, at which time the oi-normal con tacts 309 open the circuit for the motor magnet.

The sequence of operations which occur following the seizure of the called line by the ilnal selector switch depends upon whether this line is found idle or busy. Thus, at the time the called line |00' is seized by the switch, the slow-torelease relay 330 is still operated so that a circuit is prepared at the armature 33| and its associated contact 333 for energizing the busy relay 350. Now, if the called line is busy, ground is present on the control conductor |31, whereas, if the called line is idle, battery is present on this conductor. Hence, if the line is busy at the time it is seized, the above-noted circuit for energizing the busy relay 350 is completed, this circuit extending from ground on the conductor |31, by way of the springs 333 and 334, the conductor |40, the operated armature 33| and associated contact 333, the conductor |42 and through the winding of the relay 350 to battery. This relay, upon operating, interrupts, at its armature 352 and associated contact 353, a point .in the circuit i'or energizing the lower winding of the relay 310 and prepares, at this same armature and the associated contact 354, an alternative circuit for holding itself operated when the slow-to-release relay 330 restores; the alternative circuit noted extending from ground on the control conductor by way of the operated armature 352 and associated contact 354, the conductor I4|, the contact 333, the armature 334, the conductor |42, and through the winding of the busy relay to battery. The busy relay 350, upon operating, also applies, at its armature 35|, busy tone current to the loop extending through the operated selector switch |04 and the operated line switch |03 to the calling subscribers substation to indicate to the calling party thereat the busy condition of the called line. When this occurs, the calling party may, by hanging up, interrupt the loop holding the line relay 300 operated, thereby to cause the hold relay 3|0 to restore. This latter relay, upon restoring its armatures 3|| and 3|2, removes ground from the control conductors and |00 and from the hold conductor |43, whereupon the relays 250 and 350, and the magnets 260, 240, 330 and 330 are deenergized and the switch train leading to the called subscribers line is released.

It is pointed out that during the release of the final selector switch |05, the line relay 300 upon restoring its armature 304 completes, at the contact 306, a circuit for energizing the motor magnet 301 and at its armature 310| a circuit for energlzing the relay 320. Both the magnet 301 and the relay 320 are only energized for a short interval, the circuits noted being interrupted when the hold relay 3I0 restores its armatures 3|5 and '3| 1. The relay 320 during the short period when operated completes a circuit for energizing the relay 330 which also operates. 'I'he short period of energization of the magnet 301 may be sumcient to cause the wipers 3|5' and 3|6' to be stepped to their first off-normal positions, such that the ofi-normal springs 309 are closed. In order to prevent the stepping switch comprising the wipers noted from remaining in off-normal positions an alternative circuit for energizing the magnet 301 by way of the contacts 303 is provided, this circuit being completed when the relays 3|0 and 330 are de-energized and extending from ground at the armature 3|6 by way of the armature 331, the conductor |43, the otr-normal springs 309, the self-interrupting contacts 308 and through the winding of the magnet 301 to battery. 'I'his circuit is interrupted at the offnormal springs 309 following the return of the stepping switch to its normal position. Thus, a safeguard is provided for preventing the stepping switch from being falsely retained in an offnormal position when the iinal selector switch is released.

In the event the called line |00 is idle at the .time it is seized by the iinal selector switch- |05, battery is present on the control conductor |31 and the busy relay 350 is not energized over the above-traced circuit. Shortly after the seizure of the line, and when the relay 330 restores, a circuit is completed for energizing the lower winding of the relay 310, this circuit extending from battery on the control conductor |31, by way of 'the operated springs 393 and 334, the conductor |40, the armature 33| and its associated contact 332, the conductor |39, the lower winding of the relay noted, the conductor |44 and the restored armature 352, to ground on the control conductor III. The relay 310 operates, upon the energization of its lower winding, to complete, at its armature 313, an obvious locking circuit for itself, extending from ground on the conductor |43. At its armature 31|, it applies ground to the conductor |40 leading to the control conductor |31, thereby to mark the called line as busy at the contact sets to whichA it is multipled and, at its armature 312, it opens a point in the previously traced original circuit for energizing the hori; zontal magnet 380. At its armature 314, the relay 310, upon operating, applies ground to the conductor |46 and, at its armature 315, it applies ground to the ringing machine start conductor I6I. At its armatures 311 and 316 the relay 310 completes paths for applying ringing current and ring-back tone current to the loops extending respectively to the called subscribers substation and the calling subscribers substation.

Ringing current is conducted to the signal device at the called subscribers substation B over a path including the armature 311, conductor |53, the lower winding of the ring cut-off relay 360, the conductor |52, the contact 362 and its associated restored armature 36|, the conductor |33, the operated springs 362 and 39|, the line conductor |35, signal device bridged across the line conductors |35 and |36 at the called substation, the line conductor |36, the operated springs 392 and 363 and the conductor |34 and extending to ground on the restored armature 364 and its associated contact 365. A portion of ythis current is by-passed by way-oi the armature 313, the condenser |62 and the loop extending back to the calling subscribers substation to the receiver at f this substation, thereby to indicate to the calling party that the called telephone is idle. It is noted that the relay 360 is so constructed that it does not operate in response to the energization of its lower winding by the alternating ringing current.

When the called party answers, a direct current path is bridged across the line conductors |35 and |36 at the called substation, thereby to complete a direct current circuit for energizing the lower winding of the ring cutoiI relay 360, which circuit is identical with that traced above for the ringing current and extends from battery'on the conductor |53 to ground at the armature 364. In response to the energization of its lower winding, the relay 360 partially operates to complete the X contacts associated with its armature 361, thereby to cause the energization of its upper winding. When this upper winding is energized, the relay 360 fully operates to interrupt, at its armature 363, the start circuit for the ringing machine and to interrupt, at its armatures 36| andk 364 and their respective associated contacts 362 and 365, the application oi ringing current and ring-back tone current to the loops extending respectively to the called and calling subscribers' substations.` At these last mentioned armatures and their respective associated contacts 363 and 366, the calling line is connected to the called line so that a conversational circuit is completed between the calling telephone A and the called telephone B. It is pointed out that talking battery is supplied to the loop extending to the called subscribers substation through the windings of the impedance element 395, which windings are connected in series with the exchange battery across the conductors |3| and |32. Similarly, talking` battery is supplied to the loop extending to the calling subscribers substation through the windings of the line relay 300. The system remains in this condition until the connection is cleared out at the calling subscribers substation.

If the called party hangs up rst, nothing occurs, the entire switch train being held in its operated condition by virtue of the fact that the relay 300 is maintained energized over the closed loop extending therefrom to the calling substation, the hold relay 3|0 is held operated by the line relay 300, and the relays 360 and 310 are locked in their respective operated positions due to the presence of ground on the conductor |43. When, however, the calling party hangs up his receiver to interrupt the circuit holding the line relay 300 energized, this relay restores to open the operating circuit for the hold relay 3|0. The hold relay, upon restoring its armature 3| I, removes ground from the conductor |43, thereby to interrupt the holding circuits for the magnets 300 and 390 and the relays 360 and 310. At its armature 3| 2, the hold relay removes direct ground from the control conductor HI. The two relays 360 and 310 in turn restore and the last mentioned thereof removes, at its armature 31|, ground `from the conductor |40. When the magnets 330 and 390 are de-energized, they restore all of the armatures and contact springs, associated respectively therewith, to-their respective normal positions. The relay 310, upon restoring its armature 31| to remove ground from the conductor I 40, completely removes ground from the control conductor thereby to interrupt the circuits holding the magnets 240 and 200 and the relay 250 operated. Thus, the selectorswitch |04 is released. Removal oi ground from the control conductor |00 permits the line switch |03 to restore to normal, whereupon the entire switch train utilized in setting up the connection between the. substations A and B is released and all of the switches involved therein are ready for further use.

From the fo'regoing description oi the system, it wf..l be apparent that the stepping switch includci in each of the automatic selector switches |04 and |05 is operable from a normal position to a plurality of oir-normal positions, each of which corresponds to a particular group of trunk lines to which the switch |04 has access and also to a particular trunk line in each group. Thus, when the stepping switch is operated to its first oil-normal position such that the wipers 201 to 209, inclusive, stand in engagement with their respective associated third contacts, it is conditioned to select the group of trunk lines which terminate at the contact sets under the control of the vertical magnet 240 and also to select the third trunk line in this group. It follows, therefore, that each of the contacts of the set 2|4 is associated with a particular group of outgoing trunk lines and that each of the contacts of the set 2|5 is associated with a particular trunk line in each group.

Following the group selection, as described above, the means comprising the vertical magnet 240, the slow-to-release relay 230 and the motor magnet 205 automatically operates to step the stepping switch to a second position to select a particular trunk line, corresponding to an idle nal selector switch, in the selected group of trunk lines. This last mentioned means is under the control of means comprising the polarized relay 250 which renders the motor magnet 205 inoperative to continue to step the wipers 201 to 209, inclusive, in the event the trunk line in the selected group of trunk lines and corresponding to the position of the stepping switch at the conclusion of the group selection, is idle. Immediately upon the completion of the iinal selection, the means comprising one of the horizontal magnets, such, for example, as the magnet 260, operates, to establish a connection between the line 06', incoming to the switch |04, and the selected outgoing line.

It will further be apparent that the stepping switch of the final selector switch |05, while similar' to that of the intermediate selector switch |0'4 in that each off-normal position thereof corresponds to a particular group of subscribers lines and a particular line in each group, differs therefrom in the manner of its control. This difference resides in the fact that the stepping switch of the final selector switch |05 is repeatedly operated from its normal position to one or more of its off-normal positions to select a particular group of subscribers lines including the called line and to select the particular called line of the selected group of lines.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is contemplated in the appended claims to cover all such modications as fall within the true spirit and scope of the invention.

I claim:

1. An automatic switch comprising two sets of contacts, actuating means individual to each of said sets of contacts for moving the corresponding set of contacts from one position to a second position, said contact sets being so arranged relative to each other that the corresponding contacts of the respective sets engage only when the contacts oi both of said sets are moved to their respective second positions, a stepping switch, impulse responsive means for causing the operation of said stepping switch to predetermined positions, and means including said stepping switch for successively energizing said actuating means.

2. An automatic switch comprising a group of contacts arranged in sets, actuating means common to said group of contacts `for moving the same from one position to a second position, a second group oi contacts arranged in sets, actuating means common to said second group' of contacts for moving the same from one position to a second position, the contacts of said first-named group being so arranged relative to the contacts of said second group that when the contacts of both of said groups are moved to their respective second positions the contacts of a single set included in said first-named group engage the contacts of a single set included in said second group, a stepping switch, impulse responsive means for causing the operation of said stepping switch to predetermined positions, and means including V said stepping switch for successively energizing said actuating means.

3. An automatic switch comprising a rst group of contacts, actuating means for moving the contacts oi' said group from one position to a second position, a plurality of groups of contacts, each of said groups of contacts being arranged in sets, actuating means individually associated with each of said plurality of groups of contacts for moving the contacts of the corresponding group from one position to a second position, the contacts of said first group of contacts being so arranged relative to the contacts of said plurality of groups of contacts that when said rst-named actuating means and a selected one of said last-named actuating means are energized one set of contacts of said rst group engages one set of contacts included in the group of contacts with which said selected one of said actuating means is associated, a stepping switch, impulse responsive means for causing the operation of said stepping switch to predetermined positions, and means including said stepping switch for successively energizing said first-named actuating means and a selected one of said lastnamed actuating means.

4. An automatic switch comprising a plurality of groups of contacts, actuating means individually associated with each of said groups of contacts for moving the contacts of the corresponding group from one position to a second position, a plurality of additional groups of contacts, actuating means individually associated with each of said last-named groups of contacts, the contacts of each of said groups being arranged in sets and the contacts of said rst-named plurality of groups of contacts being so arranged relative to the contacts of said last-named plurality of groups of contacts that when a selected one of said first-named. actuating means and a selected one of said last-named actuating means are energized one set of contacts of the contact group associated with said selected one of said firstnamed actuating means engages one set of contacts of the contact group associated with said selected one of said last-named actuating means,

ia stepping switch, impulse responsive means for causingthe operation of said stepping-switch to predetermined positions, and means including said stepping switch for successively energizing a selected one of said first-named actuating means and a selected one of said last-named actuating means.

5. An automatic switch comprising a pair of members, a group of contacts associated with each of said members, each of said groups of contacts being arranged in sets and adapted to be moved by the corresponding member, actuating means comprising a magnet individually associated with said members for moving the corresponding member from one position to a second position, said members being so arranged relative to each other that when both`th`ereof are moved to their respective second positions the contacts of a single set of contacts associated with one of said members engage the contacts of a single set of contacts associated with the other of said members, circuits for energizing said magnets, a stepping switch, impulse responsive means for causing the operation of said stepping switch to predetermined positions, and means including said stepping switch for completing said circuits.

6. An automatic switch comprising a ilrst member, a group of members, a group of contacts associated with each oi said members, each of said groups of contacts being arranged in sets and adapted to be moved by the .corresponding member, actuating means comprising a magnet individually associated with each of said members for moving the corresponding member from one position to a second position, said iirst member being so arranged relative to said group of members that when the magnet associated therewith and one of the magnets associated with one of the members of said group of members are energized, the contacts of a single set of contacts of the group associated with said first member engage the contacts ofv a single set of contacts ofthe group associated with said one member of said group of members, circuits for energizing said magnets, a stepping switch, impulse responsive means for causing the operation of said stepping switch to predetermined positions, and means including said stepping switch for successively energizing the mag- .net associated with said first member and a selected one of the magnets individually associated with each of the members of said group of members.

7. An automatic switch comprising a plurality of members divided into two groups, a group of contacts associated with each of said members, each of said groups of contacts being arranged in sets and adapted to be moved by the corresponding member, actuating means comprising a magnet associated with each of said members for moving the' corresponding member from one position to a second position, control means for selectively energizing said magnets, the members of one of said groups being so arranged relative to the members in the other of said groups that when the magnet associated with a selected one of the members of one group and the magnet associated with a selected one of the members of the other group are energized the contacts of a single set of contacts associated with said one of said members of said one group engages the contacts of a single set of contacts associated with said one of said members of the other group.

8. In a signalling system, a plurality of lines, an automatic switch having access to said lines. said switch comprising a stepping switch operable to a plurality of positions, each of said positions corresponding to a group of said plurality of lines and a particular line in each group,

means including means responsive to a predetermined number of received impulses for operating said stepping switch to one of said positions to select a particular group of lines, and means operative following the selection of said group of lines for operating said` stepping switch to a second position to select a particular line in said selected group of lines.

9. In a signalling system, a plurality of lines, an automatic switch having access to said lines, said automatic switch comprising a stepping switch including a plurality of sets of contacts and wipers individually associated with said contact sets, each contact of one of said sets being associated with a group of said plurality of lines and each contact of a second set being associated with a particular line in each of said group of lines, a motor magnet for driving said wipers,

-series of received impulses to drive said wipers until the wiper associated with said one contact set engages the. contact associated with the one group of lines corresponding to the impulses of said series of impulses, and means for thereafter energizing said motor magnet to drive said wlpers until the wiper associated with said second contact set engages the contact associated with a particular desired line in said one group of lines.

10. In a signalling system, a plurality of lines, an automatic switch having access to said lines, an incoming line to said switch, said switch comprising a stepping switch operable to a plurality of positions, each of said positions corresponding to a group of said plurality of lines and a particular line in each group, means including means responsive to a predetermined series of received impulses for operating said stepping switch to one of said positions to select a particular group of lines, means operative following the selection of said particular group of lines for operating said stepping switch to a second position to select a particular line in said selected group of lines, and means automatically operative following the selection of said particular line for establishing a connection between said incoming line and said particular line.

11. In a signalling system, a plurality of lines, an automatic switch having access to said lines, an incoming line to said switch, said automatic switch comprising -a stepping switch having a plurality of sets of contacts and wipers individually associated with said contact sets, each contact of one of said sets being associated with a group of said plurality of lines and each contact of a second set being associated with a particular line in each of said groups of lines, a motor magnet for driving said wipers, means for energizing said motor magnet in accordance with a predetermined series of received impulses to drive said wipers until the wiper associated with said one set engages the contact associated with the one group of lines corresponding to the impulses of said series of impulses, means for thereafter energizing said motor magnet to drive said wipers until the wiper associated with said second contact set engages a contact associated with a particular line of said one group of lines there- 75 by to select said particular line, and means rethe selection of said group of lines for operating sponsive to the selection of said particular line "t said stepping switch to a second Voff-normal posifor establishing a connection between said incoming line and said particular line.

12. In a signalling system, an automatic switch comprising a plurality of groups of contact sets, a plurality of additional groups of contact sets, actuating means individually associated with each of said groups of contact sets for moving the contacts of the contact sets included in the corresponding group from one position to a second position, a plurality of lines individual ones of which terminate at individual contact sets of said second-named plurality of groups of contact sets, an incoming line to said switch, said incoming line terminating at each of the contact sets of said first-named plurality of groups of contact sets, a stepping switch included in said automatic switch and operable to a plurality of positions, each of said positions corresponding to one of the actuating means associated with one of the groups of contact sets included in said first-named plurality of groups of contact sets and to one of the actuating means associated with one of the groups of contact sets included in said second-named plurality of groups of contact sets, means including means responsive to a predetermined series of received impulses for operating said stepping switch to one of said positions, the actuating means for moving the contacts included in. one group of said first-named plurality of groups and corresponding to Asaid position being energized when said switch is operated to said one position, whereby a particular group of said plurality of lines is selected, means operative following the selection of said particular group for operating said switch to a second position, the actuating means for moving the contacts included in one group of said second-named plurality of groups and corresponding to said second position being energized to connect said incoming line to a particular line in said selected group of lines when said switch is operated to said second position.

13. In a signalling system, a plurality of lines, an automatic switch having access to said lines, said switch comprising a stepping switch having a normal position and being operable to a plurality of olf-normal positions, each of said oinormal positions corresponding to a group of said plurality of lines and to a particular line in each group, means including means responsive to a predetermined series of received impulses for operating said stepping switchv to one of said off-normal positions to select a particular group of lines, means operative following the selection of said group of lines for operating said stepping switch to a second off-normal position to select a particular line in said selected group of lines, and means automatically operative immediately following the selection of said particular line for restoring said stepping switch to normal.

14. In a signalling system, a plurality of lines, an automatic switch having access to said lines, an incoming line to said switch, said switch comprising a stepping switch having a normal position and a plurality of oli-normal positions, each of said off-normal positions corresponding to a group of said plurality of lines and to a particular line in each group, means including means responsive to a predetermined series of received impulses for operating said stepping switch to one of said off-normal positions to select a particular group of lines, means operative following tion to select a particular line in said selected group, means automatically operative following the selection of said particular line' for establishing a connection between said incoming line and said particular line, and means automatically operative immediately following the selection of said particular line for restoring saidstepping switch to normal.

15'. In a telephone system a plurality oi selector switches, an additional selector switch having access to each of said plurality of selector switches, said additional switch comprising a stepping switch having a plurality of positions, each of said positions corresponding to a group of said plurality of selector switches and to a particular switch in each group, means including means responsive to a predetermined series of received impulses for operating said stepping switch to one of said positions to select a particular group of said plurality of selector switches, and means for causing said switch to continue operating from position to position until it stands in a position corresponding to an idle switch in said selected group.

16. In a telephone system a plurality oi' selector switches, an additional selector switch having access to each of said plurality of selector switches, said additional switch comprising a stepping switch having a plurality of positions, each of said positions corresponding to a group of said plurality of selector switches and to a particular switch in each group, means including means responsive to a predetermined series of received impulses for operating said stepping switch to one Vof said positions to select a particular group of said plurality of selector switches, means for causing said switch to continue operating from position to position until it stands in a position corresponding to an idle switch in said selected group, and means for rendering said last-named means inoperative in the event the selector switch in said selected group of selector switches and corresponding to said one position of said stepping switch is idle.

17. In a telephone system, a plurality of selector switches, an additional selector switch having access to each of said plurality of switches, an incoming line to said additional switch, said additional switch comprimng a stepping switch having a plurality of positions, each of said positions corresponding to a group of said plurality of selector switches and to a particular switch in each group, means including means responsive to a predetermined series of received impulses for op-v ing to said one position of said stepping switch'.

ing a normal position and a plurality of off-normal positions, each of said off-normal positions corresponding to a group of said plurality of selector switches and-to a particular switch in each group, means including means responsive to a series of received impulses for operating said stepping switch t one of said olf-normal positions to select a particular group of said plurality of selector switches, means for causing said stepping switch to continue operating from position to position until it stands in an ofi-normal position corresponding to an idle selector switch in said selected group, means for rendering said Fast-named means inoperative in the event the selector switch in said selected group and corresponding to said one position of said stepping switch is idle, means operative when an idle selector switch in said selected group is found for connecting said incoming line through to said idle selector switch, and means operative when said idle selector switch is found for restoring said stepping switch to its normal position 19. In a signalling system, a plurality of lines, an automatic switch having access to said lines, said switch comprising a stepping switch having a normal position and a plurality of off-normal positions, each of said olf-normal positions corresponding to a group of said lines and to a particular line in each group, and means including means responsive to successive series of received impulses for repeatedly operating said stepping switch between its normal position and one or more of its off-normal positions to select a particular group of lines and a particular line in the selected group of lines.

20. In a signalling system, a plurality of lines, an automatic switch having access to said lines, said switch comprising a stepping switch having a normal position and a plurality of oil-normal positions, each of said oi-normal positions corresponding to a group of said lines and to a particular line in each group, and means including means responsive to successive series of received impulses for repeatedly operating said stepping switch between its normal position and one or more of its off-normal positions to select a particular group of lines and a particular line in the selected group of lines, said last-named means being operative immediately following the selection of said particular line to restore said stepping switch to its normal position.

21. In a signalling system, a plurality of lines, an automatic switch having access to said lines, said switch comprising a stepping switch having a normal position and a plurality of oli-normal positions, each of said oil-normal positions corresponding to a group of said plurality of lines and to a particular line in each group, means including means responsive to one predetermined series of received impulses for operating said ,stepping switch to one of said oil-normal positions to select a particular group of said lines, and means operative following the selection of said group of lines for returning said stepping switch to its normal position, said first-named means being thereafter responsive to a second predetermined series of impulses to reoperate said stepping switch to one of its olf-normal positions to selecta particular line in said selected group of lines.

22. In a signalling system a plurality of lines, an automatic switch having access to said lines, said switch comprising a. stepping switch having a normal position and a plurality of olf-normal positions, each of said oil-normal positions corresponding to a group of said plurality oi' lines and to a particular line in each group, means including means responsive to one predetermined series of received impulses foroperating said stepping switch to one of said off-.normal positions to select a particular group of said lines, means operative following the selection of said group of lines for returning said stepping switch to its normal position, said iirst-named means being thereafter responsive to a second predetermined series of impulses to reoperate said stepping switch to one of its onf-normal positions thereby to select a particular line in said selected group of lines, and means automatically operative immediately following the selection of said line for again restoring said stepping switch to normal.

23. An automatic switch comprising a plurality of contact sets, common means for moving said plurality of contact sets from one position to a second position, a first additional contact set, means for moving said nrst additional contact set from one position to a second position, a second additional contact set, means for moving said second additional contact set from one position to a second position, said contact sets being so arranged relative to each other that one contact set of said plurality of contact sets engages said ilrst additional contact set when both of these contact sets are moved to their respective second positions and that another contact set of said plurality of contact sets engages said second additional contact set when both of these contact sets are moved to their respective second positions, and means operable in response to the movements of said plurality of contacts and one of said additional contact sets to their respective second positions for preventing the movement of the other of said additional contact sets to its second position.

24. An automatic switch comprising a plurality of contact sets, common means operative to move said plurality of contact sets from one position to a second position, a first additional contact set, a first additional means operative to move said ilrst additional contact set from one position to a second position. a second additional contact set, a second additional means operative to move said second additional contact set from one position to a second position, said' contact sets being so arranged relative to each other 'that one contact set of said plurality of contact sets engages said first additional contact set when both of these contact sets are moved to their respective second positions 'and that another contact set of said plurality of contact sets engages said second additional contact set when both of these contact sets are moved to their respective second positions, and means operable after the operation of said common means and in response to the operation of one of said additional means for preventing the operation of the other of said additional means.

25. An automatic switch comprising a plurality of contact sets, common means operative to move said plurality of contact sets from one position to a second position, a rst additional contact set, means including a ilrst magnet operative to move said ilrst additional contact set from one position to a second position, a second additional contact set, means including a second magnet operative to move said second additional contact set from one position to a second position, said contact sets being so arranged relative 7a to each other that one contact set of said plurality of contact sets engages the first additional contact set when both of these contact sets are moved to their respective second positions and that another contact set of said plurality of contact sets engages said second additional contact set when both of these contact sets are moved plurality of contact sets engages the rst addi-l to their respective second positions, circuits for energizing said magnets, and means operable after the operation of said common means and in response to the operation of one of said magnets for controlling the energizing circuit of the other of said magnets to prevent the operation thereof.

26. An automatic switch comprising a plurality of contact sets, common means operative to move said plurality of contact sets from one position to a second position, a rst additional contact set, means including a first magnet operative to movesaid first additional contact set from one position to a second position, a second additional contact set, means including a second magnet operative to move said second additional contact set from one position to a second position, said contact sets being so arranged relative to each other that one contact set of said tional contact set when both of these contact sets are moved to their respective second positions and that another contact set of said plurality of contact sets engages said second additional contact set when both of these contact sets are moved to their respective second positions, circuits for energizing said magnets, and means operable after the operation of said common means and in response to the operation of one of said magnets for interrupting the energizing circuit of the other of said magnets to prevent the operation thereof.

27. An automatic switch comprising a plurality of contact sets, common means operative to move said plurality of contact sets from one position to a second position, a first additional contact set, a rst additional means operative to move said rst additional contact set from one position to a second position, a second additional contact set, a second additional means operative to move said second additional contact set from one position to a second position, said contact sets being so arranged relative to each other that one contact set of said plurality of contact sets engages said first additional contact set when both of these contact sets are moved to their respective second positions and that another contact set of said plurality of contact sets engages said second additional contact set when both of these contact sets are moved to their respective second positions, a stepping switch, impulse responsive means for causing the operation of said stepping switch to predetermined positions, means including said stepping switch for successively operating said common means and a selected one oi said additional means, and

means responsive to the operation of said selected one of said additional means for preventing the operation of the other of said additional means.

28. In a signalling system, an automatic switch including a group of contact sets, an incoming line connected to each contact set of said group, a plurality of additional contact sets, outgoing lines individually connected to said additional contact sets, common actuating means operative to move the contact sets of said group from one position to a second position, actuating means individually associated with each of said additional contact sets for moving the corresponding additional lcontact set from one position to a second position, said contact sets being so arranged relative to each other that one contact set of said group engages a corresponding one of said additional contact sets when both of these contact sets are moved to their respective second positions, impulse responsive means for operating -said common actuating means, testing means responsive to the operation oi said common actuating means for selecting an idle one of said outgoing lines, and means responsive to the selection of an idle one of said outgoing lines by said testing means for operating'said actuating means individually associated with the one of said additional. contact sets connected to the selected outgoing line..

29. In a signalling system, an automatic switch including a group of movablecontact sets, an incoming line connected to each contact set of said group, a plurality of additional movable contact sets, outgoing lines individually connected to said additional contact sets, test contact sets individually associated with said additional contact sets, testing circuits individually connected to said test contact sets, common actuating means operative to move the contact sets of said group from one position to a second position, actuating means individually associated with each of said additional contact sets for moving the corresponding additional contact set from one position to a second position, said contact sets being so arranged relative to each other that the contact sets of said group engage said test contact sets individually associated therewith when the contact sets of said group are moved to their second positions and that one contact set of said group engages one of said additional contact sets when both of these contact sets are moved to their respective second positions, impulse responsive means for operating said common actuating means, testing means including said testing circuits for selecting an idle one of said outgoing lines, and means responsive to the selectionof an idle one of said outgoing lines by said testing means for operating said actuating means individually associated with the one of said additional contact sets connected to the se- JOHN WICKS.

lected idle outgoing line. 

